When an electromagnetic radiation or an optical wave is propagated in a medium, it can be scattered inelastically by acoustic phonons inside the material. This process is known as Brillouin scattering. Brillouin scattering involves acoustic phonons, which may be different from Raman scattering that involves vibrational or rotational phonons.
Spontaneous Brillouin scattering involves acoustic phonons that may be present in a material by thermally-induced density fluctuations. Brillouin scattering can be further enhanced, stimulated, or forced by one or multiple optical pump waves with strong intensity. The magnitude and frequency of Brillouin-scattered light, or its optical spectrum, can be determined by characteristics of the acoustic phonons inside the material. The latter may be closely related to mechanical properties of the medium, such as modulus and hypersonic damping coefficient. Such viscoelastic properties therefore may be measurable by examining the Brillouin scattered light. This technique is referred to as Brillouin spectroscopy. Various techniques to detect the Brillouin signal have been widely applied in physics, material science, and mechanical engineering.
Prior Brillouin scattering studies have been also performed on biological samples, such as collagen fibers, cornea, and crystalline lens, ex vivo, as described in J. M. Vaughan and J. T. Randall, “Brillouin-Scattering, Density and Elastic Properties of the Lens and Cornea of the Eye,” Nature, vol. 284, pp. 489-491, 1980, R. Harley, D. James, A. Miller, and J. W. White, “Phonons and Elastic-Moduli of Collagen and Muscle,” Nature, vol. 267, pp. 285-287, 1977, and J. Randall and J. M. Vaughan, “Brillouin-Scattering in Systems of Biological Significance,” Philosophical Transactions of the Royal Society of London Series a-Mathematical Physical and Engineering Sciences, vol. 293, pp. 341-348, 1979. However, the potential of using Brillouin scattering for tissue biomechanics and tissue engineering has not been significantly explored, possibly because of long acquisition times required by the spectral analysis.
Accordingly, there is a need to overcome the deficiencies described herein above, and to provide improved apparatus, systems and processes for analyzing tissue biomechanics using Brillouin techniques.